1. Field of the Invention
The present invention relates to a belt tightener for tightening a belt to firmly hold heavy loads in a given fastened position on a transportation means under a sufficient frictional tension force. More particularly, the present invention relates to a belt tightener wherein a combination of a supporting member and permanent fixed and sliding bars of a specific structure for frictionally tensioning a flexible belt is adopted to tie down heavy loads such as large cars, machines or cargo containers to fastening structures provided on a transportation means such as a carrier vessel or a cart. The belt tightener prevents any arbitrary movement of such heavy loads resulting from resulting in loosening of the holding belt due to shaking of the transportation means while the heavy loads are fastened thereto.
2. Description of the Prior Art
A variety of belt tighteners have previously been designed from the or tightly holding cargo and like objects in a given position of a transportation means. One of the recent models of this type is disclosed, for example, in Japanese Laid-open Utility Model Appln. No. Sho. 61-49150. In this belt tightener, a main body, a sub-body provided with a guide member, and a lever provided with two shafts fixed thereto are journaled mutually rotatably and a belt with one free end and a hook on the other end is inserted into the guide member and around the periphery of one of the shafts fixed to the lever, wound on the other shaft and pulled out through a space formed between the shafts, then through a clearance between the one shaft and the belt wound around the periphery thereof and finally through the guide member. When the lever is in an unlocked position, the belt can easily be introduced into the tightener through a sufficiently spread space between the shafts and pulled in either direction for locking or unlocking without any frictional resistance. When the lever is moved to its locked position, however, the belt is overlapped with each other around the other shaft whereby a frictional force is acted on the belt to tighten it. This belt tightener is widely used for holding heavy cargo such as motor vehicles to fastening structures of a transportation means such as a carrier vessel or cart.
However, the belt tightener of this type has a drawback that when this tightener is used to hold considerably heavy loads such as a large size motor vehicle in a given fastening position of a carrier vessel, the frictional force necessary to tension the belt becomes insufficient especially during rough seas when the vessel is significantly rolling or pitching. Thus inadvertent slackening of the belt by slipping occurs permitting very dangerous arbitrary movement of the heavy loads on the deck of the vessel.
Under the circumstances, there is a great demand in the field of transportation for developing a new type of belt tightener in which the above mentioned drawback is fully overcome.